Giant magnetoresistance sensor with stitched longitudinal bias stacks and its fabrication process

ABSTRACT

A giant magnetoresistance (GMR) magnetic head that includes a GMR read sensor with a stitched longitudinal bias (LB) stack. The GMR read sensor includes seed, pinning, pinned, spacer, sense and cap layers in a read region, and its seed and pinning layers are extended into two side regions. The LB stack is fabricated on the pinning layer in the two side regions and includes separation, seed and LB layers. The separation layer, preferably made of an amorphous film, separates the pinning layer from the seed and LB layers and thereby prevents unwanted crystalline effects of the pinning layer. Monolayer photoresist patterning and chemical mechanical polishing may be incorporated into the fabrication process of the GMR head to attain uniform thicknesses of the separation, seed and LB layers, and to align the midplane of the LB layer at the same horizontal level as the midplane of the sense layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/229,491 filed Aug. 27, 2002 now U.S. Pat. No. 6,876,525.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a read head for a hard diskdrive, and more particularly to a giant magnetoresistance (GMR) readhead including a GMR read sensor in a read region and stitchedlongitudinal bias (LB) stacks in two side regions.

2. Description of the Prior Art

In a commonly used giant magnetoresistance (GMR) read head, a GMR readsensor is located in a read region, while a longitudinal bias (LB) stackand a conductor are located in each of two side regions. The GMR readsensor typically comprises nonmagnetic seed layers, an antiferromagneticpinning layer, ferromagnetic pinned layers, a nonmagnetic spacer layer,a ferromagnetic sense layer, and nonmagnetic cap layers. The LB stacktypically comprises a nonmagnetic seed layer and a hard-magnetic LBlayer. The conductor typically comprises highly electrically conductingnonmagnetic layers.

The LB layer must exhibit a high coercivity (H_(C)) and thus provide anLB field for stabilizing the sense layer. This stabilization scheme isthe most effective when the midplane of the LB layer is located at thesame horizontal level as the midplane of the sense layer. In the priorart head fabrication process, however, the LB stack is typicallydeposited on an amorphous Al₂O₃ bottom gap layer in the side regions toprevent some unwanted microstructural effects that causes a decrease inH_(C), and thus the midplane of the LB layer is located at a horizontallevel significantly lower than the midplane of the sense layer. As aresult, it is difficult to stabilize the sense layer.

There is therefore a need for a head fabrication process in which the LBlayer can exhibit a high H_(C) and its midplane can be located at thesame horizontal level as the midplane of the sense layer, so that themost effective stabilization of the sense layer can be obtained.

SUMMARY OF THE INVENTION

The present invention is an improved GMR read head for a hard diskdrive, in which the LB stack is stitched on the lower portion of a GMRread sensor in each of two side regions. The GMR read sensor includes anantiferromagnetic pinning layer that is extended into the two sideregions. The LB stack is stitched on the pinning layer in each of twoside regions, and it includes an amorphous nonmagnetic separation layer,a nonmagnetic seed layer exhibiting a body-centered-cubic (bcc)structure, and a hard-magnetic LB layer exhibiting ahexagonal-centered-cubic (hcp) structure.

In order to eliminate unwanted effects from the microstructures of thepinning layer, the present invention utilizes the amorphous separationlayer to separate the pinning layer from the rest of the LB stack ineach of the side regions. On top of the amorphous separation layer, thenonmagnetic seed layer grows freely, exhibiting the bcc structure withits closest packed crystalline planes lying in the film surface. On topof the nonmagnetic seed layer, the LB layer grows epitaxially,exhibiting the hcp structure with preferred crystalline planes lying inthe film surface and thus exhibiting a high coercivity (H_(C)).

In the preferred embodiment, the amorphous separation layer preferablycomprises a tungsten nitride (WN_(X)) film, where x ranges from 36 to 46at %. The nonmagnetic seed layer preferably comprises a tungsten (W)film. The head fabrication process is thereby simplified in that asingle W target can be utilized to reactively deposit the WN_(X) film inmixed gases of argon and oxygen, and to directly deposit the W film inthe argon gas. The LB layer preferably comprises a Co-xPt or Co-xPt-yCrfilm, where x ranges from 10 to 50 at % and y ranges from 1 to 20 at %.Through the use of the present invention, the LB stack can now bedeposited on top of the pinning layer. In addition to obtaining a highH_(C) for the LB layer, the midplane of the LB layer can be located atthe same horizontal level as the midplane of the sense layer of the GMRread sensor.

It is an advantage of the GMR read head of the present invention that ahead fabrication process has been developed to improve a sensorstabilization scheme.

It is another advantage of the GMR read head of the present inventionthat a head fabrication process has been developed, where the LB stackcan be deposited on top of the pinning layer of the GMR sensor in eachof two side regions.

It is further advantage of the GMR read head of the present inventionthat a head fabrication process has been developed, where the midplaneof the LB layer can be located at the same horizontal level as themidplane of the sense layer.

It is yet another advantage of the GMR read head of the presentinvention that a head fabrication process has been developed, where ionmilling is applied to only remove the upper portion of the GMR readsensor and thus the lower portion of the GMR read sensor in-situprotects the bottom gap layer from exposing to air.

It is an advantage of the hard disk drive of the present invention thatit includes a GMR read head fabricated to improve a sensor stabilizationscheme.

It is another advantage of the hard disk drive of the present inventionthat it includes a GMR read head, in which the LB stack is deposited ontop of the pinning layer in each of two side regions.

It is further advantage of the hard disk drive of the present inventionthat it includes a GMR head, in which the midplane of the LB layer islocated at the same horizontal level as the midplane of the sense layer.

It is yet another advantage of the hard disk drive of the presentinvention that it includes a GMR read head, in which the lower portionof the GMR read sensor in-situ protects the bottom gap layer fromexposing to air in the head fabrication process.

These and other features and advantages of the present invention will nodoubt become apparent to those skilled in the art upon reading thefollowing detailed description which makes reference to the severalfigures of the drawings.

IN THE DRAWINGS

FIG. 1 is a top plan view generally depicting a hard disk driveincluding a GMR read head of the present invention;

FIG. 2 is a side cross-sectional view depicting a GMR read head duringthe fabrication process of the GMR read head, as is known in the priorart;

FIG. 3 is a side cross-sectional view depicting a GMR read head aftercompleting the fabrication process of the GMR read head, as is known inthe prior art;

FIG. 4 is a chart showing the coercivity (H_(C)) versus the thickness(δ) of the Co—Pt—Cr film deposited on various seed layers used in theprior art;

FIG. 5 is a side cross-sectional view depicting a GMR read head duringthe fabrication process of the GMR read head, as is used in the firstembodiment of the present invention;

FIG. 6 is a side cross-sectional view depicting a GMR read head aftercompleting the fabrication process of the GMR read head, as is used inthe first embodiment of the present invention;

FIG. 7 is a chart showing the coercivity (H_(C)) versus the thickness(δ) of the Co—Pt—Cr film deposited on various seed layers used in thepresent invention;

FIG. 8 is a side cross-sectional view depicting a GMR read head duringthe fabrication process of the GMR read head, as is used in the secondembodiment of the present invention;

FIG. 9 is a side cross-sectional view depicting a GMR read head aftercompleting the fabrication process of the GMR read head, as is used inthe second embodiment of the present invention;

FIG. 10 is a side cross-sectional view depicting a TMR read head duringthe fabrication process of the TMR read head, as is used in the thirdembodiment of the present invention;

FIG. 11 is a side cross-sectional view depicting a TMR read head aftercompleting the fabrication process of the TMR read head, as is used inthe third embodiment of the present invention.

DETAILED DESCRIPTION OF THE FIRST EMBODIMENT

FIG. 1 is a top plan view that depicts significant components of a harddisk drive 10. The hard disk drive includes an air bearing slider thatincludes a magnetic head 20 generally comprising an Al₂O₃—TiC substrate,the GMR read head of the present invention, and a write head. The harddisk drive 10 also includes a hard disk 12 on which a magnetic medium isdeposited. The hard disk is rotatably mounted upon a motorized spindle14. An actuator arm 16 is pivotally mounted within the hard disk drive10 with the magnetic heads 20 disposed upon a distal end 22 of theactuator arm 16. A typical hard disk drive 10 may include a plurality ofhard disks 12 that are rotatably mounted upon the motorized spindle 14and a plurality of actuator arms 16 having magnetic heads 20 mountedupon the distal ends 22 of the actuator arms 16. As is well known tothose skilled in the art, when the hard disk drive 10 is operated, thehard disk 12 rotates upon the motorized spindle 14 and the air bearingslider is flying above the surface of the rotating hard disk 12.

FIG. 2 is a side cross-sectional view depicting a GMR read head duringthe fabrication process of the GMR read head, as is known in the priorart, and FIG. 3 is a side cross-sectional view depicting a GMR read headafter completing its fabrication process as is known in the prior art.This prior art fabrication process is improved in the present invention,and FIGS. 2 and 3 therefore serve as a suitable starting point for thedescription of this invention.

A wafer 40 used in the fabrication process typically comprises an ˜1.2mm thick Al₂O₃—TiC ceramic substrate 40 coated with a ˜6 μm thick Al₂O₃film. In the fabrication process, as is depicted in FIG. 2, a bottommagnetic shield layer (S₁) 42, preferably formed of a 1 μm thick Ni—Fefilm, is deposited on the wafer 40. To fabricate a GMR read head withits sense layer located in the midplane of a 80 nm thick read gap, abottom gap layer (G₁) 46, preferably formed of a 10.6 nm thick Al₂O₃film, is deposited on the S₁ 42. Thereafter, multiple seed layers 50,preferably comprising a 3 nm thick Al₂O₃ film, a 3 nm thick Ni—Cr—Fefilm, and a 1 nm thick Ni—Fe film, are then sequentially deposited onthe G₁ 46. The Al₂O₃ film used as the G₁ 46 is preferably directlysputtered in an argon gas from an Al₂O₃ target, while the Al₂O₃ filmused as the seed layer is preferably reactively sputtered in mixed argonand oxygen gases from an Al target. A pinning layer 54, preferablycomprising a 15 nm thick Pt—Mn, is then deposited on the multiple seedlayers 50. Thereafter, pinned layers 58, preferably comprising a 1.6 nmthick Co—Fe film, a 0.8 nm thick Ru film and a 1.8 nm thick Co—Fe film,are deposited on the pinning layer 54. A spacer layer 62, preferablyformed of a 2.2 nm Cu—O film, is deposited on the pinned layers 58.Thereafter, a sense layer 66, preferably formed of a 2 nm Co—Fe film, isdeposited on the spacer layer 62. Cap layers 70, preferably comprising a0.6 nm thick Cu film and 6 nm thick Ta film, are then deposited on thesense layer 66.

After the depositions, the wafer is annealed in a 10 kOe magnetic fieldperpendicular to an alignment mark for 5 hours at 265° C. Bilayerphotoresists, comprising a lower photoresist 80 and an upper photoresist84, are then applied and exposed in a photolithographic tool to mask theGMR read sensor in a read region 88 for defining a sensor width, andsubsequently developed in a solvent to form undercuts 94. The GMR readsensor in unmasked side regions 96 is removed by ion milling until theG₁ 46 is exposed. With reference to FIG. 3, the LB stack 102, preferablycomprising a 3 nm thick Cr film and a 40 nm thick Co—Pt—Cr film, is thendeposited onto the unmasked side regions 96. Thereafter, the conductor106, preferably comprising a 3 nm thick Cr film and a 80 nm thick Rhfilm and a 3 nm thick Ta film, is also deposited also onto the unmaskedside regions 96. These depositions of the LB stack 102 and the conductor106 create overhangs 100 upon the sides of the photoresist 84. Thebilayer photoresists are then lifted off. Subsequently, the GMR readsensor is patterned for defining a sensor height, connected with arecessed conductor (preferably comprising a 3 nm thick Ta film, a 80 nmthick Cu film and a 3 nm thick Ta film), covered by a top gap layer (G₂)110 formed of a 32.4 nm thick Al₂O₃ film, and a second magnetic shieldlayer (S₂) 114.

After the completion of this fabrication process of the GMR read head,the fabrication process of the write head starts. After the completionof the fabrication processes of the GMR read and write heads, the GMRread and write heads are lapped along the alignment mark until designedsensor height and throat height are attained.

In fabricating the read head, to ensure good electrical and magneticcontacts of the GMR read sensor with the LB stack 102 and the conductor106, ion milling of the GMR read sensor is typically applied by tiltingan ion beam gun by 10° from a normal line for the formation of two shortsensor edges 116, and the depositions of the LB stack 102 and theconductor 106 are conducted by tilting an ion beam gun by 20° from thenormal line for good coverage over the sensor edges. The two shortsensor edges 116 are needed to prevent unwanted domain instability,while the good coverage is needed to ensure sufficient thickness of theLB stack 102 and the conductor 106 at the sensor edges 116 and to ensurea steady electrical flow without an electrostatic discharge.

It is difficult for this prior art GMR read head to stabilize the senselayer 66, due to severe ion milling applied to the GMR read sensor inthe unmasked side regions and shadowing effects of the bilayerphotoresists with the overhangs 100 formed during the depositions of theLB stack 102 and the conductor 106. Severe ion milling creates a deeptrench in the unmasked side regions, and thus the midplane 120 of the LBlayer 102 deposited on the G₁ 46 within the deep trench is located farbelow the midplane 124 of the sense layer 66. Shadowing effects causethe deposited films to form “tapers” at the sensor edges 116, and thusthe designed film thicknesses cannot be attained at the sensor edges.Particularly, the Cr seed layer of the LB stack 102 cannot be thickenough or even does not exist at sensor edges 116, and a Co—Pt—Cr LBlayer deposited on a Cr seed layer thinner than 1.5 nm cannot exhibit ahigh H_(C). In addition, the Co—Pt—Cr LB layer cannot be thick enough oreven does not exist at the sensor edges, so that it is difficult toattain a designed H_(C) high enough to suppress domain activities at thesensor edges 116 and a designed magnetic moment comparable to that ofthe sense layer 66. As a result, an LB field induced from the LB layer102 is generally not high enough to adequately stabilize the sense layer66.

To solve these issues in the prior art fabrication process, the Cr seedand Co—Pt—Cr LB films that are deposited on the G₁ layer within the deeptrench are much thicker than would otherwise be designed. The thicknessof the Cr seed layer increases from 1.5 to 3 nm, while the thickness ofthe Co—Pt—Cr hard magnetic film increases from 12.8 to 40 nm(corresponding to three and nine times of the magnetic moment of thesense layer, respectively). As shown in FIGS. 3 and 4 (discussedherebelow), with such thick Cr seed and Co—Pt—Cr LB films, parts of theCr and Co—Pt—Cr “tapers” can be located above the midplane 124 of thesense layer 66, and the Cr and Co—Pt—Cr “tapers” are thick enough tostabilize the sense layer 66. However, when the sense layer isstabilized, very high magnetic moments in the unmasked side regionscause substantial decreases in signal sensitivity and read efficiency.

As is well known to those skilled in the art, the Co—Pt—Cr hard magneticfilm requires an underlying Cr film to attain a high in-plane coercivity(H_(C)) in order to stabilize the sense layer. FIG. 4 shows H_(C) versusthe Co—Pt—Cr film thickness for Co—Pt—Cr and Cr(3)/Co—Pt—Cr films(thickness in nm) deposited on an Al₂O₃-coated substrate. The use of theunderlying Cr film leads the Co—Pt—Cr film to exhibit an H_(C) of beyond1000 Oe. An X-ray diffraction pattern (not shown) taken from theCo—Pt—Cr film indicates that it grows “freely” on the amorphous Al₂O₃film, exhibiting a hexagonal-centered-cubic (hcp) structure (a=0.256 nmand c=0.407 nm) with its closest packed {0001} crystalline plane lyingin the film surface. Another X-ray diffraction pattern (not shown) takenfrom the Cr/Co—Pt—Cr films indicates that the Cr film grows “freely” onthe amorphous Al₂O₃ film, exhibiting a body-centered-cubic (bcc)structure (a=0.290 nm) with its closest packed {110} crystalline planeslying in the film surface, and the Co—Pt—Cr film then grows“epitaxially” on the Cr film, exhibiting the hcp structure mainly with{01 10} or {01 11} crystalline planes lying in the film surface. The useof the Cr film thus causes the <0001> c-axis of the Co—Pt—Cr hcpstructure (the easy axis of magnetization) to lie in the film surface,in order to achieve lattice matching between the Cr bcc {011} and theCo—Pt—Cr hcp {01 10} (or {01 11}) crystalline planes. Due to thisepitaxial growth, in-plane magnetic properties of the Co—Pt—Cr film,including H_(C), are thus improved.

It is crucial not to leave any polycrystalline films in the unmaskedside regions before the depositions of the Cr/Co—Pt—Cr films, sincethese polycrystalline films may affect the “free” growth of the Cr filmand the wanted “epitaxial” growth of the Co—Pt—Cr film, thusdeteriorating its in-plane magnetic properties. For example, if thePt—Mn film 54 is left in the side regions, the Co—Pt—Cr and Cr/Co—Pt—Crfilms deposited thereon will exhibit a low H_(C). FIG. 4 also showsH_(C) vs Co—Pt—Cr film thickness for Pt—Mn(15)/Co—Pt—Cr andPt—Mn(15)/Cr(3)/Co—Pt—Cr films deposited on the Al₂O₃-coated substrate.The existence of the underlying Pt—Mn film 54 leads the Co—Pt—Cr andCr/Co—Pt—Cr films to exhibit an H_(C) of below 400 Oe. X-ray diffractionpatterns (not shown) taken from the Co—Pt—Cr and Cr/Co—Pt—Cr filmsindicate that the growth of the Cr and Co—Pt—Cr films is severelyaffected by the underlying Pt—Mn film, which exhibits aface-centered-tetragonal (fct) structure with its closest packed {111}crystalline plane lying in the film surface. The closest atomic distancein the Pt—Mn fct {111} crystalline plane (0.272 nm) is greater than thatin the Cr bcc {110} crystalline plane (0.251 nm) and that in theCo—Pt—Cr {01 10} or {crystalline plane (0.256 nm). As a result, thislattice mismatching leads to a low H_(C).

As is next described with the aid of FIGS. 5 and 6, the GMR read head200 of the present invention provides a solution to the problems justdescribed. FIG. 5 is a side cross-sectional view depicting a GMR readhead during the fabrication of the first embodiment of the presentinvention, and FIG. 6 is a side cross-sectional view depicting a GMRread head after completing the fabrication process of the firstembodiment of the present invention. In contrast to the prior art GMRread head depicted in FIGS. 2 and 3 that is confined in the read region,the lower portion of the GMR read head of this invention, includingAl₂O₃/Ni—Cr—Fe/Ni—Fe/Pt—Mn films, is extended into the two side regions96. In order to eliminate unwanted effects of microstructures of thelower portion of the GMR read sensor, an amorphous film 206, such asWN_(X), is used as a separation layer to separate the lower portion ofthe GMR read sensor from the LB stack in each of the side regions. Ontop of the amorphous separation layer 206, a nonmagnetic film 210, suchas W, and a Co—Pt—Cr hard magnetic film 212 are deposited.

In the fabrication process, as is depicted in FIG. 5, an S₁ layer 42 anda G₁ layer 46, preferably formed of a 1 μm Ni—Fe film and 10.6 nm thickAl₂O₃ film, respectively, are sequentially deposited on a wafer.Thereafter, a GMR read sensor 214, preferably comprisingAl₂O₃(3)/Ni—Cr—Fe(3)/Ni—Fe(1)/Pt—Mn(15)/Co—Fe(1.6)/Ru(0.8)/Co—Fe(1.8)/Cu—O(2.2)Co—Fe(2)/Cu(0.6)/Ta(6)films (thickness in nm), is then deposited on G₁ layer 46. After thedepositions, the wafer is annealed in a 10 kOe magnetic fieldperpendicular to an alignment mark for 5 hours at 265° C. Bilayerphotoresists, comprising a lower photoresist 80 and an upper photoresist84, are then applied and exposed in a photolithographic tool to mask theGMR read sensor in a read region 88 for defining a sensor width, andsubsequently developed in a solvent to form undercuts 94. Significantly,the GMR read sensor in unmasked side regions 96 is only partiallyremoved by ion milling until the Pt—Mn film 54 is exposed. An LB stack,preferably comprising a 3 nm thick WN_(X) film 206, a 3 nm thick W film210 and a 40 nm thick Co—Pt—Cr hard magnetic film 212, is then depositedonto the unmasked side regions. Thereafter, the conductor 218,preferably comprising Cr(3)/Rh(80)/Ta(3) films, is also deposited ontothe unmasked side regions 96. The bilayer photoresists are then liftedoff. Subsequently, as depicted in FIG. 6, the GMR read sensor 214 ispatterned for defining a sensor height, connected with a recessedconductor (preferably comprising a Ta(3)/Cu(80)/Ta(3) films), covered bya top gap G₂ layer 224 formed of a 32.4 nm thick Al₂O₃ film. A topshield layer (S₂) 228 preferably formed of a 1 μm thick Ni—Fe film isthen deposited on the wafer. After photolithographic patterning of theS₂ layer into designed shapes and thus completing the fabricationprocess of the GMR read head 200, the fabrication process of the writehead starts. After the completion of the fabrication processes of theGMR read and write heads, the GMR read and write heads are lapped alongthe alignment mark until designed sensor height and throat height areattained, and the magnetic head of the present invention is completed.

Significantly, in the present invention, an amorphous film, such as theWN_(X) film 206, is successfully used as a separation layer to separatethe Pt—Mn film 54 from the W and Co—Pt—Cr films 210 and 212 respectivelyin each of the side regions, thereby eliminating unwanted effects ofmicrostructure of the Pt—Mn film and maintaining a high H_(C). FIG. 7shows H_(C) versus the Co—Pt—Cr film thickness for W(6)/Co—Pt—Cr,Pt—Mn(15)/W(6)/Co—Pt—Cr and Pt—Mn(15)/WN_(X)(3)/W(3)/Co—Pt—Cr filmsdeposited on an Al₂O₃-coated substrate. The use of the underlying W film210 leads the Co—Pt—Cr film to exhibit an H_(C) of beyond 1,000 Oe. AnX-ray diffraction pattern taken (not shown) from the W/Co—Pt—Cr filmsindicates that the W film grows “freely” on the amorphous Al₂O₃ film,exhibiting a bcc structure (a=0.317 nm) with its closest packed {110}crystalline planes lying in the film surface, and the Co—Pt—Cr film thengrows “epitaxially” on the W film, exhibiting the hcp structure mainlywith {01 10} or {01 11} crystalline planes lying in the film surface.The use of the W film 210 thus also causes the <0001> c-axis of theCo—Pt—Cr hcp structure (the easy axis of magnetization) to lie in thefilm surface, in order to achieve lattice matching between the W bcc{011} and the Co—Pt—Cr hcp {01 10} (or {01 11}) crystalline planes. Dueto this epitaxial growth, in-plane magnetic properti of the Co—Pt—Crhard magnetic film 212, including H_(C), are thus improved.

It is significant that, if mild ion milling is applied so that the Pt—Mnfilm 54 is left in the side regions 96, and W/Co—Pt—Cr films aredeposited thereon, the W/Co—Pt—Cr films exhibit a low H_(C) due tounwanted lattice mismatching. This unwanted lattice mismatching iseliminated when the amorphous WN_(X) film 206 separates the Pt—Mn film54 from the W and Co—Pt—Cr films, 210 and 212 respectively. Since themild ion milling only creates a shallow trench in the unmasked sideregions, the midplane 230 of the Co—Pt—Cr film 212 deposited on theWN_(X)/W films within the shallow trench is located closer to themidplane 124 of the sense layer. As a result, an LB field induced fromthe Co—Pt—Cr film 212 can be high enough to stabilize the sense layer66. In addition, the Co—Pt—Cr film 212 does not need to be very thick inorder to stabilize the sense layer, and thus signal sensibility canremain high.

The mild ion milling also plays a crucial role in in-situ protecting thebottom gap layer G₁ 46 with the seed layer 50 and the residual Pt—Mnfilm 54 in the side regions, thereby protecting the bottom gap layer G₁from air contamination. As a result, the probability of shorting betweenthe bottom shield layer S₁ and the GMR read head can be substantiallyreduced.

In this first embodiment, the conducting, amorphous WN_(X) film 206 isselected as the amorphous separation layer. A preferred as-depositedWN_(X) film 206 with nitrogen contents x ranging from 36 to 46 at % hasan electrical resistivity of 200 μΩ-cm and is amorphous. The WN_(X) film206 remains amorphous after annealing at temperatures below 500° C., andcrystallization from the amorphous phase into a W₂N compound occursafter annealing at 525° C. Other metallic films (e.g. W—Re films with Recontents ranging form 50 to 75 at %) can also be considered as theamorphous separation layer 206.

DETAILED DESCRIPTION OF THE SECOND EMBODIMENT

To more precisely locate the midplane 230 of the LB layer 212 at thesame horizontal level as the midplane 124 of the sense layer 66 and toensure uniform thicknesses of the separation, seed and LB layers at thesensor edges, photolithographic patterning with a monolayer photoresistis used in this second embodiment. FIG. 8 is a side cross-sectional viewdepicting a GMR read head during the fabrication process of thisembodiment, and FIG. 9 is a side cross-sectional view depicting a GMRread head after completing the fabrication process of this secondembodiment. As with the first embodiment, the lower portion of the GMRread head is extended into the two side regions 96, however, in thissecond embodiment the midplane 230 of the LB layer 212 is located at thesame horizontal level as the midplane 124 of the sense layer 66, and thethicknesses of the separation, seed and LB layers are uniform at thesensor edges.

In the fabrication process of the second embodiment, as is depicted inFIG. 8, an S₁ 42 and a G₁ 46, preferably formed of a 1 μm Ni—Fe film and10.6 nm thick Al₂O₃ film, respectively, are sequentially deposited on awafer. Thereafter, a GMR read sensor 304, preferably comprisingAl₂O₃(3)/Ni—Cr—Fe(3)/Ni—Fe(1)/Pt—Mn(15)/Co—Fe(1.6)/Ru(0.8)/Co—Fe(1.8)/Cu—O(2.2)/Co—Fe(2)/Cu(0.6)/Ta(1.8)films (thickness in nm), is then deposited on the G₁ 42. An electricallyinsulating layer 308, preferably formed of a 18 nm thick SiO₂ film, isthen deposited on the GMR read sensor 304. After the depositions, thewafer is annealed in a 10 kOe magnetic field perpendicular to analignment mark for 5 hours at 265° C. A monolayer photoresist 312 isthen applied and exposed in a photolithographic tool to mask the GMRread sensor in a read region 316 for defining a sensor width, andsubsequently developed to remove the monolayer photoresist in theunmasked side regions 320. Reactive-ion-etching (RIE) is applied tocompletely remove the electrically insulating layer 308 in the unmaskedside regions, and ion milling is then applied to remove the upperportion of the GMR read sensor until the Pt—Mn film 54 is exposed. Themonolayer photoresist 312 is then lifted off. Subsequently, as isdepicted in FIG. 9, the LB stack, preferably comprisingWN_(X)(3)/W(3)/Co—Pt—Cr(12.8) films, 324, 328 and 332 respectively, isthen deposited on the entire wafer. Chemical mechanical polishing (CMP)is then applied to the entire wafer until the SiO₂ film 308 is exposedand its thickness is reduced from 18 to 3 nm. Since the SiO₂ film istransparent, its thickness can be precisely monitored by anellipsometer. Bilayer photoresists are then applied and exposed in aphotolithographic tool to mask the GMR read sensor in a read region andpart 340 of the LB stack, and subsequently developed in a solvent toform undercuts. The conductor 344, preferably comprisingTa(3)/Rh(80)/Ta(3) films, is then deposited onto the unmasked regions.The bilayer photoresists are then lifted off. Subsequently, the GMR readsensor is patterned for defining a sensor height, connected with arecessed conductor (preferably comprising a Ta(3)/Cu(80)/Ta(3) films),covered by a top gap layer G₂ 346 preferably formed of a 33.6 nm thickAl₂O₃ film. A top shield layer (S₂) 348, preferably formed of a 1 μmthick Ni—Fe film, is then deposited on the wafer. Afterphotolithographic patterning of the S₂ into designed shapes and thencompleting the fabrication process of the GMR read head 300, thefabrication process of the write head starts. After the completion ofthe fabrication processes of the GMR read and write heads, the GMR readand write heads are lapped along the alignment mark until designedsensor height and throat height are attained to complete the fabricationof the integrated read/write heads of the magnetic head 300 of thissecond embodiment.

In this second embodiment, the midplane 352 of the LB layer 332 can beprecisely located at the same horizontal level as the midplane 124 ofthe sense layer 66 by partial ion milling of the Pt—Mn film 54 in theside regions and CMP of the SiO₂ film 308 to a desired thickness. Inaddition, due to the nonexistence of shadowing effects in forming the LBstack, a uniform thickness of the separation 324, seed 328 and LB layers332 can be attained at the sensor edges. Hence, the seed and Co—Pt—Crfilms deposited within the shallow trench can be the same as designed.Particularly, the deposited Co—Pt—Cr hard magnetic film 332 can be asthin as 12.8 nm (corresponding to a magnetic moment of three times ofthe sense layer 66), but the magnetic moment at the sensor edges canalready be higher than that of the sense layer 66. As a result, thesense layer is stabilized, and high signal sensitivity and high readefficiency can be maintained.

DETAILED DESCRIPTION OF THE THIRD EMBODIMENT

The fabrication process of the GMR read head as described in the secondembodiment of the present invention can also be applied to thefabrication process of a tunneling magnetoresistance (TMR) read headwhich will play a more crucial role in ultrahigh density magneticrecording. FIG. 10 is a side cross-sectional view depicting a TMR readhead 400 during the fabrication process of this third embodiment of thepresent invention, and FIG. 11 is a side cross-sectional view depictinga TMR read head 400 after completing the fabrication process of thisthird embodiment of the present invention.

In the fabrication process, as is depicted in FIG. 10, a bottom shieldlayer (S₁) 42, preferably formed of a 1 μm thick Ni—Fe film, isdeposited on a wafer. Thereafter, a TMR read sensor 404, preferablycomprisingTa(3.2)/Ni—Fe(1)/Pt—Mn(20)/Co—Fe(1.6)/Ru(0.8)/Co—Fe(1.8)/Al—O(0.6)/Co—Fe(2)/Cu(0.6)/Ru(8.4)films is then deposited on the S₁ 42. An electrically insulating layer,preferably formed of a 18 nm thick SiO₂ film 408, is then deposited onthe TMR read sensor. After the depositions, the wafer is annealed in a10 kOe magnetic field perpendicular to an alignment mark for 5 hours at265° C. A monolayer photoresist 412 is then applied and exposed in aphotolithographic tool to mask the TMR read sensor in a read region 418for defining a sensor width, and subsequently developed to remove themonolayer photoresist 412 in the unmasked side regions 422.Reactive-ion-etching (RIE) is applied to completely remove the SiO₂ filmin the unmasked side regions 422, and ion milling is then applied toremove the upper portion of the TMR read sensor until the Pt—Mn film 54is exposed. The monolayer photoresist 412 is then lifted off.Subsequently, as is depicted in FIG. 11, the LB stack 426, preferablycomprising WO_(Y)(3)/W(3)/Co—Pt—Cr(12.8) films, is then deposited on theentire wafer. Chemical mechanical polishing (CMP) is then applied to thewafer until the SiO₂ film 408 is completely removed. Since the SiO₂ filmis transparent, any unwanted residual SiO₂ film can be detected by anellipsometer. A 23.6 nm thick Ta film 432 and a top shield layer (S₂)436, preferably formed of a 1 μm thick Ni—Fe film, are then sequentiallydeposited on the wafer. After photolithographic patterning of the S₂into designed shapes and then completing the fabrication process of theTMR read head 400, the fabrication process of the write head starts.After the completion of the fabrication processes of the TMR read andwrite heads, the TMR read and write heads are lapped along the alignmentmark until designed sensor height and throat height are attained, andthe integrated read/write heads of the third embodiment completed.

In this embodiment, the insulating, amorphous WO_(Y) film 440, where Yis approximately 10 to 50 at. %, is selected as a separation layer sinceit is not prone to chemical etching used in the photolithographicpatterning process. In contrast to the conventional used Al₂O₃ filmwhich is partially removed by chemical etching and thus cannot act as agood separation layer, the WO_(Y) film which stays intact after chemicaletching appears to be a much more robust separation layer. In additionto the WO_(Y) film, many other insulating, amorphous films, such asSiO₂, CrO_(X), etc., can also be selected as separation layers. It iscrucial to ensure good insulation of selected separation layers, so thata sense current can only flow through the thin Al—O barrier layer toexhibit desired TMR effects.

While the present invention has been shown and described with regard tocertain preferred embodiments, it will be understood that those skilledin the art will no doubt develop certain alterations and modificationsthereto which nevertheless include the true spirit and scope of theinvention. It is therefore intended that the following claims cover allsuch alterations and modifications.

1. A method for fabricating a magnetic head comprising: fabricating aplurality of thin films to create a read sensor, said read sensorincluding seed, pinned, pinning, spacer, ferromagnetic sense and caplayers having a central portion and outwardly disposed end portions;milling said plurality of thin films such that a central sensor regionis protected from milling and unprotected outer regions are milled downto said pining layer; fabricating a longitudinal bias (LB) stack uponsaid pinning layer at said outer regions such that said LB stack isdisposed proximate said end portions of said sense layer; wherein saidLB stack is fabricated including the steps of depositing an amorphousfilm upon said pinning layer, and depositing a nonmagnetic film uponsaid amorphous film, and depositing a hard magnetic film upon saidnonmagnetic film, wherein said nonmagnetic film has a bcc crystallinestructure; and wherein said amorphous film is comprised of a materialselected from the group consisting of WN_(x), where x is approximately36 to 46 at. %, W—Re where Re is approximately 50 to 75 at. %, andWO_(Y) where Y is approximately 10 to 50 at. %.
 2. A method forfabricating a magnetic head as described in claim 1 wherein saidnonmagnetic film is comprised of a material selected from the groupconsisting of W or a W-based alloy, Cr and a Cr-based alloy, and whereinsaid pinning layer is comprised of Pt—Mn, and said hard magnetic film iscomprised of Co—Pt—Cr or Co—Pt.
 3. A method for fabricating a magnetichead as described in claim 2 wherein said amorphous film has a thicknessof from approximaiely 1 nm to approximately 10 nm, and wherein saidnonmagnetic film has a thickness of from approximately 1 nm toapproximately 10 nm.
 4. A method for fabricating a magnetic head asdescribed in claim 3 wherein said amorphous film has a thickness ofapproximately 3 nm and said nonmagiaetic film has a thickness ofapproximately 3 nm.